1. Field of the Invention
The present invention relates to an optical scanning probe device in which low-coherence light is guided and is made to exit to living-body tissue, and reflected light therefrom is guided so as to produce an optical tomogram.
2. Description of Related Art
In recent years, in the case where living-body tissue is diagnosed, in addition to an imaging device to gain optical information regarding the surface condition of the tissue, an optical CT device which can gain optical information regarding the inside of the tissue has been suggested.
In this optical CT device, picosecond pulses are used for detecting information regarding the inside of a living body and, therefore, a tomogram is produced. However, a laser light source, which emits very short-pulsed light on the order of picosecond pulse, is expensive and is large, and cumbersome handling is required.
Recently, OCT (Optical∘Coherence∘Tomography) which produces a tomogram of test specimen by the use of low-coherence light has been disclosed in, for example, PCT Japanese Translation Patent Publication No. 6-511312 (U.S. Pat. No. 5,312,501).
Japanese Unexamined Patent Application Publication No. 11-56786 has disclosed in detail an optical scanning probe device which can be used by insertion through an endoscope.
However, as is shown in FIG. 4, etc., in the publication of Japanese Unexamined Patent Application Publication No. 11-56786, since the optical scanning probe device of the prior example is nearly in the shape of a cylinder, it is difficult, for example, to observe at a given distance from the living-organic tissue.
That is, it is possible to observe while the outer surface of the sheath is in contact with the surface of the living-body tissue. However, it is difficult to observe while the outer surface of the sheath is held at a position some distance from the living-body tissue surface larger than that in the aforementioned condition.
In the prior example, specifically designed optical scanning probe devices having different focus positions have been used in accordance with methods for observation and parts to be observed. Consequently, many specifically designed optical scanning probe devices have been required and therefore, a large burden has been born by the user. Furthermore, the management thereof has been cumbersome.
In the OCT device of the prior example, an observation target is radiated with a light beam for performing observation, and relative position relationship between the focus position of this light beam and the observation target is an important parameter for producing a tomogram of the OCT.
Since the beam diameter becomes minimum at the focus position of the light beam, information with the highest resolution can be gained at this part. Therefore, for example, when the focus position is located on the surface of the observation target, detailed information can be gained in the neighborhood of the surface. When the focus position is located inside the observation target, detailed information regarding the deep part can be gained.
In the case where the observation target has an intense light scattering characteristic, when the focus position coincides with the surface of the observation target, an intense light scattering occurs at the observation target surface and, therefore, only reflected light from the surface may be imaged. Consequently, it may be required that the focus position is located intentionally inside the tissue surface, or is located outside in order to observe.
Furthermore, it is important that the light beam is made to enter into the observation target as perpendicularly as possible in order to gain a tomogram with precise information regarding distance.
Japanese Unexamined Patent Application Publication No. 11-56768 has disclosed in detail an optical scanning probe device which can be used by insertion through an endoscope.
In such an optical probe device, since the light beam is made to scan in the circumferential direction in order to produce a circular tomogram centering the probe, when the observation target is located at a distance from the probe as far as possible, a wide range tomogram can be produced compared to that in the observation performed while the observation target is in contact with the probe.
Therefore, the probe, in which the focus position of the light beam has been located away from the probe, has been used, the probe has been positioned at a location some distance from the observation target, and observation has been performed while the aforementioned focus position relationship has been adjusted with the angle of the endoscope and the like.
In the case where tomography observation has been performed using an optical probe and, at the same time, endoscopic therapy has been performed from the same position by the use of endo-therapy products, for example, biopsy forceps, an endoscope having two forceps channels, etc., has been used, the optical probe has been inserted through one channel so as to observe, and an endo-therapy product such as biopsy forceps, has been inserted into the other channel so as to perform therapy aiming at the scanning position of the light beam.
However, regarding an optical probe device of a conventional example which has been inserted through an endoscope as shown in FIG. 4, etc., in the publication of Japanese Unexamined Patent Application Publication No. 11-56768, it has been very difficult to perform stable positioning while fine adjustment among the observation target, light beam focus, entry angle, etc., has been made by endoscope operation in accordance with the observation purpose in the state in which the optical probe device is protruded from the endoscope tip. In addition, it has been attended with significant difficulties to perform biopsy aiming at the scanning position of the light beam by the combination of the endoscope having two forceps channels and the biopsy forceps.